Billionaire Mike Bloomberg must be grilled by lawyers in a legal fight with several ex-employees, a Manhattan judge has ruled.

Federal Judge Richard Casey ordered the mayor-elect to sit for a deposition in a lawsuit Bloomberg filed over billing practices at his company’s offices in Princeton, N.J.

Bloomberg sued ex-employee Joseph Menno and several others in 1999, charging they conspired to rip off his company by padding bills and then laundering kickbacks to each other.

The mogul accused Menno of setting up a contracting company with his brother, John, which ostensibly provided services to Bloomberg, but which he alleged was really created to overcharge Bloomberg’s financial news empire.